Add rubocop gems

Author: sue445

ruby_header_parser.gemspec

@@ -41,6 +41,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rspec-its"
   spec.add_development_dependency "rspec-parameterized"
   spec.add_development_dependency "rspec-temp_dir"
+  spec.add_development_dependency "rubocop"
+  spec.add_development_dependency "rubocop_auto_corrector"
 
   # For more information and examples about making a new gem, check out our
   # guide at: https://bundler.io/guides/creating_gem.html